Method of assembling an actuator with an internal sensor
A method of installing a piston position sensor proximate to a closed end of a hydraulic cylinder is provided. The sensor is attached to the face of a piston and that piston/sensor combination is inserted into the cylinder tube to position the sensor in the desired location. When properly located within the cylinder tube, the sensor is affixed to the cylinder tube by means of beveled holes in the sensor that receive bolts threadedly inserted through the cylinder tube to further properly align the sensor within the cylinder tube. When so affixed, the sensor is then detached from the piston so that the piston can thereafter move independently of the sensor. A fixture is also used that allows the assembler to accurately align the angular orientation of the sensor prior to being inserted into the cylinder tube.
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FIELD OF THE INVENTION
The invention generally relates to actuators having an internal moving member and an internal sensors for sensing the position of the moving member relative to a fixed reference.
This application is related to U.S. Pat. No. 6,234,061 entitled “Precision Sensor for a Hydraulic Cylinder,” and co-pending U.S. patent applications, Ser. No. 09/793,218 filed Feb. 26, 2001 entitled “Precision Sensor for a Hydraulic Cylinder,” U.S. Ser. No. 09/785,097 filed Feb. 16, 2001 entitled “Multi-Turn, Non-contacting Rotary Shaft Position Sensor,” U.S. Provisional Patent Application Ser. No. 60/351,007 filed Jan. 23, 2002 entitled “An Improved Lead Guide for Cable Extension Type Position Sensors,” and U.S. Provisional Patent Application Ser. No. 60/364,711 filed Mar. 15, 2002 entitled “Method and Apparatus for Connecting Cables” filed concurrently, having the same inventor and assignee as the present application. Each of those related applications is incorporated herein by reference.
Actuators are in wide spread use to actuate other implements or devices. The applications of actuators are virtually limitless and the size, shape, etc. of the actuator as well as the device actuated is relatively unconstrained. Hydraulic cylinders are one commonly used form of actuators. Such actuators include a cylinder and an internal piston which actuates an external device. In many actuator applications, there is a need for greater control of the movement of the device imparted by the actuator. One example of this need is in the equipment arena where hydraulic cylinders are used as actuators to control the movement of a mechanical device, such as the bucket or claw on construction equipment.
There are, in use today, various types of piston position sensors that are used to accurately sense the position of a piston within a hydraulic cylinder. The operation of such hydraulic cylinders, therefore, depends upon a position sensor to automatically and accurately determine the location of a piston with the hydraulic cylinder, and correspondingly, the position of the particular implement that is being controlled by that hydraulic cylinder. One of such sensors and its use and construction is shown and described in U.S. Pat. No. 6,234,061 entitled “Precision Sensor for a Hydraulic Cylinder,” and the disclosures of which is hereby incorporated by reference. That particular sensor is, therefore, one that is positioned within the interior of the hydraulic cylinder proximate the closed end of the cylinder, that is, the end opposite the working end where the piston rod extends to be affixed to the equipment to be moved.
In the construction and assembly of hydraulic cylinders, the manufacture of such hydraulic cylinders is an established, well-defined process. It is desirable not to disrupt that process by adding some additional complexity to the manufacturing techniques, that is, the less changes that are required in the current manufacturing practices, the better the acceptance of the sensor.
In the normal manufacturing practices of assembling a hydraulic cylinder, the final assembly consists of bringing together two major subassemblies, the “tube assembly” and the “piston rod” assembly. The tube assembly consists mainly of the cylinder tube with the back cap attached thereto and the other end is open to receive the piston rod assembly. The piston rod assembly, on the other hand, consists of the piston rod, the head and the piston. As such, in the final assembly, the piston rod assembly is inserted into the tube assembly similar to loading a cannon such that the piston is inserted into the open end of the cylinder tube and is pushed all the way back to the closed end of the cylinder tube. When so inserted the head is positioned at the open end of the cylinder tube and secured thereto, either by means of a threaded connection by threads formed internal of the cylinder tube and threads formed external to the head, or by means of bolts that are threaded into a mating flange welded to the open end of the cylinder tube. In either case, once the head has been secured to the open end of the cylinder tube, the cylinder assembly is complete.
Accordingly, it would be advantageous to provide a system or procedural steps in the manufacture of a hydraulic cylinder to be able to install a sensor in the closed end of a cylinder tube, and secure the sensor at that location while minimizing disruptions and changes to current manufacturing practices for the construction and assembly of such hydraulic cylinders.
SUMMARY OF THE INVENTION
Broadly, the present invention relates to a method of assembling an actuator having an internal moving member wherein a sensor is positioned internally with the actuator during actuator assembly. An exemplary actuator of this type is a hydraulic cylinder and piston.
In one aspect of the invention, the actuator is a cylinder and piston assembly and the sensor is of the type where a first portion, such as a flexible connector, connects to the piston, the sensor is positioned in the closed end of the cylinder. Prior to insertion, the first portion of the sensor is attached to the piston and the piston and sensor are inserted in the cylinder to the desired position. The sensor housing, or second portion, is secured to the cylinder via a second portion of the sensor. Advantageously, this assembly may be performed during the final stages of the actuator assembly without disrupting or altering the piston and cylinder manufacturing operations. That is, the initial stages of the construction of the cylinder is carried out in the conventional manner and the present invention comes into play during final assembly, when the piston rod assembly is interfitted into the cylinder tube assembly. At that point in the assembly procedure, the piston position sensor is attached to a portion of the piston, such as the distal piston face, and the sensor and piston are inserted into the cylinder during that final assembly.
In another aspect of the invention, a flexible mounting collar affixed to the top of the piston position sensor features a hexagonal, or other configured pocket, formed in the mounting collar. The flexible connector exits the top of the sensor in the center of the hexagonal pocket and the cable connector resembles a modified bolt, having a hexagonal head that is loosely fitted into and engaged by the hexagonal pocket formed in the top of the mounting collar. The hexagonal pocket feature makes the attachment of the sensor to a portion of the piston, e.g., the distal piston face, easier and more efficient as the threaded end of the attachment bolt can be engaged with the threaded receiving hole on the piston. Since the hexagonal head of the attachment bolt is secured to the hexagonal pocket on the mounting collar, the engagement of the attachment bolt with the threaded hole in the piston is accomplished by rotating the entire sensor. When the attachment bolt is substantially screwed in, the sensor can be withdrawn from the piston for a short distance to provide access to the attachment bolt, and final tightening can be accomplished.
In another aspect of the invention, the mounting collar can be attached to the distal face of the piston such that the piston position sensor is releasably affixed or attached to the distal face, that is, the face that initially enters the cylinder tube. The mounting collar is located on the outer surface of the sensor i.e. the surface that faces outwardly when in the inserted position. An internally shaped pocket is also formed on the distal face of the piston such that the mounting collar is adapted to releasably fit to the pocket in a manner that allows the fit to be later disengaged. One exemplary fit is a snap fit, but other releasable engagements can be used.
In another aspect, the mounting collar is formed as a substantially conical projection from the top of the sensor and is preferably formed of an elastomeric material and can be an integral feature of the sensor external packaging. The flexible property of the mounting collar allows the mounting collar to snap fit or otherwise engage into the cylindrical mounting pocket formed in the distal face of the piston. The mounting pocket in the distal face of the piston has annular groove around the periphery of its inner face and the mounting collar is provided with an annular ridge protruding from the outer periphery of the mounting collar and which engage with each other to releasably affix or attach the sensor to the piston.
Accordingly, after the connection of the flexible connector to the distal face of the piston has been completed, the mounting of the sensor onto the distal face of the piston is accomplished by pressing the mounting collar into the mounting pocket formed in the piston and twisting slightly until the collar snaps into the mounting pocket. The attachment is sufficient to hold the sensor to the piston during assembly of the hydraulic cylinder and is detachable after the final cylinder assembly is completed so that the piston can thereafter move independently of that portion of the sensor.
In another aspect of the invention, which is desirable for a sensor intended to have a particular angular orientation within an hydraulic cylinder, in the actual insertion of the piston rod assembly into the cylinder tube assembly, the angular alignment of the sensor is checked since certain asymmetrical features of the sensor, such as its mounting holes, should be in approximate alignment when the sensor reaches the closed end of the cylinder tube. The angular alignment relates to the angular orientation of the sensor features around the axis of the cylinder tube and that alignment is easily adjusted. The sensor collar forms a rotatable connection with the piston face and a fixture is provided to assure that the proper angular orientation is achieved before the sensor is inserted into the cylinder tube. One means of ensuring proper angular alignment of the sensor to the cylinder tube is to fix an optical beam on an assembly bench and fix the optical beam along a flat area of the sensor. Alternative methods could, of course, be used such as utilizing a gate having a flat surface that mates with a flat surface of the sensor to arrive to the correct angular orientation of the sensor with respect to the cylinder tube.
In yet another aspect, the piston rod assembly is pushed into the cylinder tube assembly by means of a push rod such the piston is pushed all the way back into the cylinder tube, thereby positioning the sensor in the desired position at the back, closed end of the cylinder tube. The sensor can be affixed in that location by means of two opposing installation bolts that are threaded from the outside of the cylinder tube through threaded holes in the cylinder tube, extending through the pressure wall and beveled engaging holes provided on each side of the sensor. The bolts are oriented perpendicular to the axis of travel of the piston and at the closed end of the cylinder tube in the sensor's operating location proximate that closed end. The engaging holes provided in the sensor are substantially opposite one another, and located to correspond with the threaded holes provided in the cylinder tube. The engaging holes provide a bevel around their open end so as to compensate for alignment errors during installation. Thus, by the beveled holes, as the bolts are secured to the holes, the bevel will steer the sensor into proper alignment and that alignment also applies to deviations in front-to-back placement of the sensor. More or less than two bolts can be used, or engagement mechanisms other than threaded engagement can be use without departing from the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the invention may be obtained from consideration of the following description in conjunction with the drawings in which:
The are also two beveled holes 130 (only one of which is shown in
Turning now to
Turning now to
Turning now to
In one aspect, the attachment bolt can be hollow, and the flexible connector can be connected to the attachment bolt by means of a ball. This will permit the bolt to rotate about the connector without twisting the connector. Such an arrangement is disclosed in a provisional U.S. Provisional Patent Application Ser. No. 60/364,711 entitled “Method and Apparatus for Connecting Cables”, which is hereby incorporated by reference.
A receiving pocket 420 is formed in the distal face 325 of the piston 320. After tightening the threaded connector 140 into the distal face 325 of the piston 320, the mounting collar 110 can be snapped into the receiving pocket 420 so that the sensor 100 is secured to the distal face 325 of the piston 320. In this way the sensor 100 is attached to the piston rod assembly 210, prior to the final assembly of the hydraulic cylinder in a connection that can later be disconnected in the further steps in carrying out the present invention.
Turning now to
Once the sensor 100 has been fully secured within the closed end 354 of the cylinder tube 350, the piston 320 can be moved away from the sensor 100 to detach itself from the sensor 100 so that thereafter the piston 320 can move freely and independent of the sensor 100 that is now in a secured position in its operative location so that the hydraulic cylinder can operate in its normal manner.
Turning now to
It is also desirable that the sensor 100 by properly aligned for insertion into the cylinder tube 350 in order to locate various physical features or components, including mounting and signal connection features of the sensor 100 in the proper aligned orientation when inserted into its operative position within the cylinder tube 350, including the alignment of the beveled holes 130 (
Thus, the light beam from the light emitter 830 will be blocked by the circular outer peripheral surface of the sensor 100, however, as the sensor 100 is rotated with respect to piston 320, there will be a point in its angular orientation where the light beam from the light emitter 830 passes along the flat face 920 where the outer peripheral surface is inset as opposed to the normal circular periphery and the light beam from the light emitter 830 will reach the light detector 835. As such, when the light detector 835 senses the light beam, the system recognizes that the sensor 100 is in the proper orientation for insertion into the cylinder tube assembly 200 and a pusher can, at the time push the piston rod assembly 210 into the cylinder tube assembly 200. The use of the light emitter 830 and detector 835 can easily be employed to provide a visual or audible signal to the effect that the sensor 100 is in the proper angular orientation.
Turning now to
In addition or in combination with the above, the flat surface can be used to simply orient the sensor to a reference. For example, during pushing, the flat surface can be used as a sight reference to maintain the sensor substantially in some orientation, such as maintaining the surface substantially horizontal. In this manner, the sensor is inserted such that it is approximately aligned for securing.
It is to be understood that the invention is not limited to the illustrated and described forms of the invention contained herein. It will be apparent to those skilled in the art that various changes may be made without departing for the scope of the invention and the invention is not considered limited to what is shown in the drawings and described in the specification.
First, for example, while the present invention has been disclosed with respect to a cylinder and included piston, the present invention is applicable to other actuators having a movable member disposed with a fixed member and wherein a portion of the sensor is attached to the movable member and which tracks movement of this member so that the sensor provides an indication of the position of the movable member relative to the fixed member.
Second, the shape of the fixed and movable members need not be circular as in the disclosed cylinder and piston, but each of these members may have virtually any shape. Second while the disclosed cylinder and piston is oftentimes an hydraulic cylinder, the term “hydraulics” referring to any of a number of fluids, i.e., one or more liquids, one or more gases or a combination of the two, the mechanism for applying force to the movable member is virtually unconstrained. Furthermore, it is recognized that a spring for example can be used to apply force to the movable member. Accordingly, for purposes of this disclosure, the term actuator shall include hydraulic cylinders and other devices having internally moving members which are moved by a variety of force imparting mechanisms, including fluids and or other arrangements.
Third, while threaded engagements are shown for attaching the flexible connector to the piston and the sensor to the cylinder, other engagements can be used without departing from the invention.
Fourth, while the exemplary embodiments demonstrate insertion of a sensor into a cylinder, other objects can also be inserted without departing from the method of the invention.
1. A method of mounting a position sensor on a hydraulic cylinder comprising:
- attaching a first portion of a sensor to a predetermined portion of a piston, the first portion of the sensor being displaceable from a second portion of the sensor, the first portion of the sensor being attached by means of a flexible member to the second portion of the sensor;
- inserting the piston and the first and second portions of the sensor into a cylinder through an open end of the cylinder; and
- securing the second portion of the sensor within the cylinder while retaining the first portion of the sensor attached to and movable with the piston.
2. The method of claim 1 comprising the further step of:
- displacing the second portion of the sensor from the first portion of the sensor, the first portion remaining attached to the predetermined portion of the piston.
3. The method of claim 2 wherein the second portion includes an element adapted to removably attach to the piston.
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Filed: Mar 15, 2002
Date of Patent: Aug 22, 2006
Patent Publication Number: 20030135995
Assignee: Control Products, Inc. (East Hanover, NJ)
Inventor: Glasson O Richard (Whippany, NJ)
Primary Examiner: Minh Trinh
Assistant Examiner: Donghai D. Nguyen
Attorney: Gibbons, Del Deo, Dolan, Griffinger & Vecchione
Application Number: 10/098,933
International Classification: B21D 53/26 (20060101); B21H 1/04 (20060101); B21H 1/08 (20060101); B23P 15/20 (20060101);